U.S. patent number 8,258,441 [Application Number 11/745,348] was granted by the patent office on 2012-09-04 for magnetic element temperature sensors.
This patent grant is currently assigned to TSI Technologies LLC. Invention is credited to Brian L. Clothier.
United States Patent |
8,258,441 |
Clothier |
September 4, 2012 |
Magnetic element temperature sensors
Abstract
Small, low-cost wireless temperature sensors (120) are provided
for sensing the temperature of servingware (121). Each temperature
sensor preferably includes a substrate (124); at least one sensor
element (122) positioned on the substrate; and an adhesive (126)
for securing the sensor element to the substrate and for securing
the temperature sensor to the servingware so that the sensor
element may sense a temperature of the servingware. The temperature
sensors may be used in conjunction with a reader/detector (136)
operable to generate a magnetic field of magnitude sufficient to
cause re-magnetization responses of the temperature sensor element
and optional data elements to detect such responses, and to use the
detected responses to determine the temperature of the servingware
by means of a decoding algorithm. The temperature sensors can be
used in closed-loop heating systems capable of controlling the
heating of the servingware.
Inventors: |
Clothier; Brian L. (Wichita,
KS) |
Assignee: |
TSI Technologies LLC (Wichita,
KS)
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Family
ID: |
41504195 |
Appl.
No.: |
11/745,348 |
Filed: |
May 7, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20100006562 A1 |
Jan 14, 2010 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60919345 |
Mar 22, 2007 |
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60836448 |
Aug 9, 2006 |
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60818385 |
Jul 5, 2006 |
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60798591 |
May 9, 2006 |
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Current U.S.
Class: |
219/494; 219/505;
324/219; 374/101; 374/163; 219/497 |
Current CPC
Class: |
G01K
1/024 (20130101); G01K 7/36 (20130101); G01K
2207/08 (20130101) |
Current International
Class: |
H05B
1/02 (20060101) |
Field of
Search: |
;219/494,497,501,504,505
;374/100,102,120,163-187 ;324/219-228,260,244,263 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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358155322 |
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Sep 1983 |
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JP |
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360069527 |
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Apr 1985 |
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JP |
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363313880 |
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Dec 1988 |
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JP |
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403205576 |
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Sep 1991 |
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JP |
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404099935 |
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Mar 1992 |
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JP |
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06277491 |
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Oct 1994 |
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JP |
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2003-211926 |
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Jul 2003 |
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JP |
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2004103286 |
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Feb 2004 |
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JP |
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2006-00320 |
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May 2006 |
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JP |
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9406553 |
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Mar 1994 |
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WO |
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Other References
US. Appl. No. 60/798,591; entitled Glass-Coated Amorphous Magnetic
Microwire Temperature Sensors. cited by other .
U.S. Appl. No. 60/818,385; entitled Glass-Coated Amorphous Magnetic
Microwire Temperature Sensors. cited by other .
U.S. Appl. No. 60/836,448; entitled Glass-Coated Amorphous Magnetic
Microwire Temperature Sensors. cited by other .
U.S. Appl. No. 60/881,866; entitled Microwire-Controlled Autoclave
and Method. cited by other .
U.S. Appl. No. 60/919,345; entitled Microwire-Controlled
Servingware Warming System and Method. cited by other .
U.S. Appl. No. 11/619,066; entitled Magnetic Element Temperature
Sensors. cited by other .
U.S. Appl. No. 11/745,348; entitled Magnetic Element Temperature
Sensors. cited by other .
Horac Chirac; Preparation and Characterization of Glass Covered
Magnetic Wires; Materials Science and Engineering A304-306, 166-71
(2001). cited by other .
Donald et al.; The Preparation, Properties and Applications of Some
Glass Coated Metal Filaments Prepared by the Taylor-Wire Process;
Journal of Material Science, 31, 1139-48 (1996). cited by other
.
Wiesner and Schneider; Magnetic Properties of Amorphous Fe--P
Alloys Containing Ga, Ge, and As; Phys. Stat. Sol. (a) 26, 71
(1974). cited by other .
Antonenko et al.; High Frequency Properties of Glass-Coated
Microwires; Journal of Applied Physics, vol. 83, 6587-89. cited by
other .
Henry et al.; Magnetic measurement of Iron-Rich Amorphous Alloys
Containing Chromium: Mossbauer Study and B-H Loops; Journal of
Material Science 19: 1000-06 (1984). cited by other .
V. Zhukova et al.; Development of thin microwires with low curie
temperature for temperature sensors applications; Sensors and
Actuators B; Cheimcal (2007); doi:10.116/j.snb.2007.02.019. cited
by other .
Fletcher et al.; Remote Interrogated Temperature Sensors Based on
Magnetic Materials; IEEE Transactions on Magnetics; vol. 36, No. 5,
Sep. 2000. cited by other .
Zhukova et al. Studies of Magnetic Properties of Thin Microwires
with Low Cure Temperature; Journal of Magnetism and Magnetic
Materials 300, 16-23 (2006). cited by other .
D. Makhnovskiy et al.; Remote Microwave Testing of Stress and
Temperature Distributions in Composite Materials Incorporating
Ferromagnetic Wires; School of Computing, Communications and
Electronics, University of Plymouth, Drake Circus, Plymouth, Devon
PL4 8AA, UK; Jun. 2007. cited by other .
International Search Report and Written Opinion dated Aug. 8, 2007;
PCT/US2005/33586. cited by other .
International Search Report and Written Opinion dated Feb. 4, 2008;
PCT/US2005/33596. cited by other .
International Search Report and Written Opinion dated May 19, 2008;
PCT/US2007/60032. cited by other .
International Search Report and Written Opinion dated Jun. 12,
2008; PCT/US2008/051827. cited by other .
International Search Report and Written Opinion dated Jun. 3, 2008;
PCT/U52007/68483. cited by other .
Office Action dated Oct. 19, 2007 in U.S. Appl. No. 11/061,345,
filed Feb. 18, 2005 entitled Food Preparation System. cited by
other .
Final Rejection dated Apr. 1, 2008 in U.S. Appl. No. 11/051,345,
filed Feb. 18, 2005 entitled Food Preparation System. cited by
other .
Office Action dated Jan. 24, 2008 in U.S. Appl. No. 11/083,432,
filed Mar. 18, 2005 entitled Boil Detection Method and Computer
Program. cited by other.
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Primary Examiner: Paschall; Mark
Attorney, Agent or Firm: Hovey Williams, LLC
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Provisional Patent
Application entitled "Microwire-Controlled Servingware Warming
System and Method," Ser. No. 60/919,345, filed Mar. 22, 2007;
Provisional Patent Application Ser. No. 60/836,448, filed Aug. 9,
2006; Provisional Patent Application Ser. No. 60/818,385, filed
Jul. 5, 2006; and Provisional Patent Application Ser. No.
60/798,591 filed May 9, 2006. Each of the foregoing applications is
incorporated by reference herein.
This application is also related to corresponding Non-Provisional
Patent Application Ser. No. 11/619,066, filed Jan. 2, 2007, and
this application is also incorporated by reference herein.
Claims
Having thus described the preferred embodiment of the invention,
what is claimed as new and desired to be protected by Letters
Patent includes the following:
1. A method of sensing the temperature of an object, the method
comprising the steps of: placing a re-magnetizable temperature
sensor in thermal contact with the object, said temperature sensor
comprising a plurality of magnetically susceptible,
temperature-sensitive sensor elements each in the form of an
elongated, amorphous metallic wire or thin strip, each of said
sensor elements having a different composition and a
correspondingly different set point temperature below a level of
about 400.degree. C.; generating an alternating magnetic field in
the region of the temperature sensor in order to induce a different
temperature-sensitive re-magnetization response from each of said
sensor elements, respectively; and detecting the re-magnetization
responses of the sensor elements, and using the detected responses
to at least in part determine whether the temperature of the object
is above or below the set point temperatures of the respective
sensor elements, said detecting step comprising the step of using
one of the sensor elements having a relatively lower set point
temperature to measure the temperature of another of the sensor
elements having a relatively higher set point temperature above the
set point temperature of said one sensor element.
2. The method of claim 1, the detecting step comprising the steps
of using a field receiving coil to detect the re-magnetization
responses and to generate output signals corresponding to the
detected re-magnetization responses.
3. The method of claim 2, further including the step of using a
signal processing unit operably coupled with the field receiving
coil to receive the output signals and to determine therefrom at
least the approximate temperature of the object.
4. The method of claim 3, including the step of determining the
temperature of the object comprising the step of determining the
temperature within a range of temperatures.
5. The method of claim 1, said object being servingware.
6. The method of claim 5, said temperature sensor oriented to
measure the temperature of food placed on said servingware.
7. The method of claim 1, said placing step comprising the step of
adhering said temperature sensor to said object.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is broadly concerned with magnetic element
temperature sensors, detectors for use with such sensors,
closed-loop heating systems making use of the sensors and detectors
to wirelessly determine the temperature of an object and to control
the object's temperature, and corresponding methods. More
particularly, the invention is concerned with temperature sensors
made up of at least one magnetically susceptible sensor element,
preferably formed of amorphous or nanocrystalline metal, and having
a re-magnetization response under the influence of an applied
alternating magnetic field which is different below and above at
least one set point temperature, such as the Curie temperature of
the sensor element. These temperature sensors can be used with
correlated detectors for temperature sensing, and as a part of
closed-loop heating systems. The temperature sensors may be
incorporated into adhesive backed stickers that can be quickly and
easily adhered to any number or type of objects, for example
servingware, so that the servingware, and food place thereon, can
be heated by a closed-loop feedback heating system.
2. Description of the Prior Art
A variety of applications for temperature sensors that can be read
wirelessly exist in the marketplace. These applications vary from
sensing and reporting the internal temperature of livestock to
being part of a closed-loop temperature feedback system that allows
a magnetic induction heater to precisely control the temperature of
insulated food delivery boxes. Many of these applications are
disclosed in U.S. Pat. Nos. 5,954,984, 6,232,585, 6,320,169,
6,953,919, and 6,208,253.
Many of those applications are currently being served by Radio
Frequency Identification (RFID) temperature sensing systems. These
RFID temperature sensing systems include an RFID reader/detector
and its associated RFID "tag," whereby the tag has some type of
temperature sensor as part of its circuitry.
These prior REID systems tend to be relatively expensive owing to
the cost of the tags, and are unable to operate continuously in
excess of 125.degree. C. Moreover, they lack the ability to
transmit information in the vicinity of metal or other conducting
materials, particularly when the RFD tag is embedded within the
conducting material.
Magnetic element markers (or "tags") are commonly used as part of
an electronic article surveillance (EAS) systems or other
authentication systems. These markers or tags are passive,
typically small, less expensive than RFID tags, can operate at high
temperatures, and in some forms, can transmit their information
wirelessly to a detector even when embedded within a conductor.
For example, EAS markers or tags made of soft magnetic amorphous
alloy ribbons are disclosed in U.S. Pat. No. 4,484,184. These
ribbons have a composition consisting essentially of the formula
M.sub.a N.sub.b O.sub.c X.sub.d Y.sub.e Z.sub.f, where M is at
least one of iron and cobalt, N is nickel, O is at least one of
chromium and molybdenum, X is at least one of boron and
phosphorous, Y is silicon, Z is carbon, "a"-"f" are in atom
percent, a ranges from about 35-85, b ranges from about 0-45, c
ranges from about 0-7, d ranges from about 5-22, e ranges from
about 0-15 and f ranges from about 0-2, and the sum of d+e+f ranges
from about 15-25. The marker ribbons are capable of producing field
perturbations at frequencies which are harmonics of the frequency
of an incident alternating magnetic field produced by a field
transmitter. A detecting means is arranged to detect magnetic field
perturbations at selected tones of the harmonics produced in the
vicinity of the interrogation zone by the presence of the marker
therewithin. Generation of harmonics by the marker is caused by
nonlinear magnetization response of the marker to an incident
magnetic field.
There is a need in the art for wireless temperature sensing systems
using small, less expensive temperature sensing elements, that can
operate continuously at temperatures in excess of 125.degree. C.,
and that have the ability to transmit information even in the
vicinity of metal or other conducting materials. Furthermore, it
would be advantageous if such improved temperature sensing elements
were able to carry predetermined data relating to the sensor itself
or to the object to be temperature sensed, e.g., the identity of
the object, object characteristics, or heating instructions.
Finally, advantages would be realized if the sensing elements could
be used as a part of a closed-loop feedback heating system able to
control the output of a heating device and thus control the
temperature of an object.
In connection with another aspect of the present invention,
restaurants and other food-serving establishments commonly use
various devices to keep servingware (dinner plates, platters,
bowls, pans, chafing dishes etc.) and the food thereon or therein
warm after the food is placed upon the servingware. For example,
plates of food prepared in restaurants must be kept warm while
other plates of food destined for the same customer are still being
prepared. Similarly, warming trays are frequently used to keep
serving platters and bowls and the food thereon warm.
The most common devices for keeping servingware and food warm are
heat lamps which use radiation from various light sources; food
wells, or steam tables, which use conduction from condensing steam
generated via energy from either a petroleum-fueled flame below, or
an electric element submerged in, a water bath below the
servingware; and microwave ovens. Unfortunately, these heating
devices are inefficient and have no convenient means to precisely
control the temperature of the servingware or food and thus
frequently overheat or underheat the servingware and food.
For example, with heat lamp systems, the lamps are on continuously,
even when there is no servingware below the lamps, thus wasting
energy and unnecessarily heating surrounding areas. Furthermore,
these systems have no temperature feedback from the food to the
heat lamp and therefore continue to heat the food after it has been
warmed above its proper temperature, resulting in overheating and
drying of the food. To reduce the likelihood of overheating, heat
lamps with reduced power ratings are sometimes used, but undersized
heat lamps often do not generate enough energy to fully heat the
servingware to a temperature high enough to keep the food thereon
warm enough. Finally, the rim of servingware placed under heat
lamps often gets hotter than desired because the heat lamps direct
light upon the rim as well as the food on the servingware. This
necessitates the use of gloves or pot holders when handling the
servingware and wastes energy used to unnecessarily heat the
rim.
Similarly, steam table systems are energy inefficient because they
have no closed loop temperature feedback. Thus, to ensure safe food
temperatures, these systems are typically operated at their highest
temperatures, wasting energy and causing the food heated by the
systems to become overheated and dried-out.
Microwave ovens also typically do not use temperature feedback
information to allow closed loop temperature control of servingware
placed therein. Some microwaves have temperature probes that can be
inserted into food to provide temperature information so as to
create a closed-loop temperature control system. However, such
wired probes are not convenient, especially for high volume
operations such as restaurants.
Thus, there is a need in the art for improved devices, systems, and
methods for maintaining the temperature of food items after they
are placed on or in servingware.
SUMMARY OF THE INVENTION
The present invention provides a wholly new class of temperature
sensors, methods of temperature sensing and closed-loop heating
systems. The invention is preferably predicated upon the discovery
that reliable temperature sensing can be obtained through use of
magnetic temperature sensing elements, each having a characteristic
re-magnetization response under the influence of an applied
alternating magnetic field, wherein the responses are
temperature-sensitive and can be readily monitored.
In more detail, a preferred temperature sensor is configured for
placement in thermal contact with an object in order to sense a
parameter related to the temperature of the object, for example the
temperature of the object, a desired temperature of the object, a
temperature range of the object, a desired temperature range of the
object, a minimum temperature of the object, a maximum temperature
of the object, a heating property of the object, and material
supported by the object. The sensor comprises at least one
magnetically susceptible sensor element having a re-magnetization
response under the influence of an applied alternating magnetic
field, the re-magnetization response being defined by at least one
short, detectible pulse of magnetic field perturbation of defined
short duration and which is different below and above at least one
set point temperature. Preferably, the set point temperature is the
Curie temperature of the sensor element, or a temperature close
(usually within about 25.degree. C.) of this Curie temperature. In
most applications, the set point temperature is below about
400.degree. C.
When such a temperature sensor element is placed in thermal contact
with an object to be temperature-sensed, and an alternating
magnetic field is applied to the sensor element of sufficient
magnitude to cause the desired re-magnetization response, the
sensor element operates in the manner of a "temperature switch."
That is, when the object is below the set point temperature of the
sensor element, a re-magnetization response from the sensor element
is observed; when the object temperature reaches or exceeds the set
point temperature, either no re-magnetization response is observed,
or the response is altered. Often, the re-magnetization response is
altered in a predictable manner in a small range of temperatures
below the set point temperature, above which the response
disappears. In such instances, the information concerning an aspect
of the altered response (such as the magnitude of the response
relative to a reference value) may be used to make a sensor element
act as an infinite temperature sensor over a small temperature
range prior to the set point temperature, and act as a temperature
switch at the set point temperature whereabove no re-magnetization
response is observed.
Normally, temperature sensors in accordance with the invention make
use of a plurality of sensor elements each having a different set
point temperature than the other sensor elements. Preferably, these
plural sensor elements are designed to have successive different
set point temperatures which vary from lowest to highest and in at
least a somewhat uniform fashion, so that the temperature of the
object can be monitored over a range of temperatures corresponding
to the design of the temperature sensors. In such a situation, the
magnitude of the differences between adjacent set points may define
the resolution of the temperature sensor.
In order to most effectively make use of the temperature sensor of
the invention, use is made of a detector correlated with the sensor
elements. Such a detector generally has a device for generating an
alternating magnetic field of sufficient magnitude to interrogate
the sensor elements (i.e., to cause re-magnetization responses of
the sensor elements based upon the temperature of the object), and
a device for detecting such responses. In practice, the detector
has a magnetic field generator coil and a field receiving coil both
coupled with a signal processing unit. In use, the detector
generates the requisite alternating magnetic field, and the field
receiving coil detects the re-magnetization responses of the sensor
elements, issuing output signals to the signal processing unit. The
signal processing unit, preferably in the form of a digital
microprocessor, employs a decoding algorithm which allows
determination of the object temperature. In preferred forms, the
decoding algorithm comprises one or more look-up tables correlating
the re-magnetization responses of the sensor elements with object
temperature.
The magnetically susceptible sensor elements are advantageously
formed as metallic bodies in an amorphous or nanocrystalline state.
Such metallic bodies are preferably in the form of very thin
elongated wires or strips having a maximum cross-sectional
dimension (e.g., diameter) of up to about 100 .mu.m, and can be
produced in a variety of manners. One particularly suitable form of
the metallic bodies is the microwire form, comprising an inner
metallic core and an optional outer glass coating. Such microwires
can be produced by the well-known Taylor method or as water-cast
amorphous bodies. However, it is not necessary to make use of
microwires in the context of the invention, so long as the sensors
include the requisite magnetically susceptible sensor elements.
In another aspect of the invention, new microwire-based composite
or combination microwires are provided. In such constructions, an
inner microwire made up of an elongated metallic body is shielded
by means of an adjacent ferromagnetic sheath of known Curie
temperature, which prevents or at least alters the re-magnetization
response of the associated microwire metallic body at temperatures
below the sheath Curie temperature (or at a known temperature close
to the sheath Curie temperature). The sheath may be located in
surrounding relationship with the inner microwire, or at least
partially disposed about the inner microwire in spaced relationship
therefrom. One particularly preferred composite microwire includes
an inner most magnetic susceptible microwire body with a
surrounding glass casing. The sheath is tubular and surrounds the
glass casing, and has an outermost glass casing around the sheath.
Such a composite design can readily be produced using a modified
Taylor method. Specifically, a pair of inner and outer glass tubes
are telescoped together with the magnetically susceptible metal
within the inner tube and the ferromagnetic sheath material between
the inner and outer tubes. These components are rendered molten and
are quickly pulled to create the desired composite structure.
In another aspect of the invention, a method of sensing the
temperature of an object is provided. This method broadly comprises
the steps of placing a temperature sensor in thermal contact with
said object, the sensor comprising at least one magnetically
susceptible sensor element having a re-magnetization response under
the influence of an applied alternating magnetic field, and wherein
the re-magnetization response is different below and above at least
one set point temperature. Next, an alternating magnetic field is
generated in the region of the sensor and of sufficient magnitude
to cause the re-magnetization response of the sensor element.
Thereupon, the re-magnetization response of the sensor element is
detected and used to at least in part determine whether the
temperature of the body (and therefore of the object) is above or
below the set point temperature (e.g., other information may be
used along with the detected re-magnetization response in the
temperature determination).
As noted previously, the sensor normally has a plurality of
magnetically susceptible sensor elements, each having a different
re-magnetization response under the influence of an applied
alternating magnetic field and each re-magnetization response being
different below and above a set point temperature, and wherein the
set point temperatures of the sensor elements are different from
each other. In such a case, the re-magnetization responses of at
least certain of the plural sensor elements are detected and used
to measure the temperature of the sensor elements and of the
object.
Where a sheathed composite or combination microwire sensing element
is used, the associated ferromagnetic sheath prevents the
re-magnetization responses of the associated microwire body by
magnetically saturating or biasing the body until the sensor
elements and the object reach a temperature above the Curie
temperature, or at some fixed temperature near the Curie
temperature, of the ferromagnetic sheath. The extent of magnetic
saturation or biasing of the sensor element by the sheath can be
designed to yield a series of different or altered re-magnetization
responses over a range of temperatures approaching the Curie
temperature of the sheath. This behavior is identical to the case
described above for the non-composite and non-combination sensor
elements. Assuming that the correlated detector has a sufficient
resolution and discrimination, these different or altered responses
can be detected and used for temperature sensing. Thus, in such a
case a single microwire sensing element can exhibit a plurality of
different set point temperatures.
The invention also provides a unique structure and method for
selectively measuring the temperature of an object made up of at
least a pair of components designed to be placed in proximity to
each other, with at least one of the components being heatable. For
example, a heater and a correlated heatable consumable item (e.g.,
an induction heater and a container filled with heatable shaving
cream) can be temperature monitored and controlled in accordance
with the invention. In such a design an induction-heatable nozzle
designed to connect to the container and to heat the fluid exiting
the container would be equipped with a temperature sensor in
accordance with the invention, whereas the container would be
equipped with a magnetic field-responsive data element (e.g., a
conventional microwire) correlated with the nozzle-applied
temperature sensor. The temperature sensor and data element are
correlated such that the re-magnetization response of the
temperature sensor can only be decoded if both the temperature
sensor and data element are simultaneously subjected to an
interrogating alternating magnetic field. This is usually
accomplished by altering the decoding algorithm of the detecting
device so that it will not detect and report object temperature
unless both the temperature sensor and data element are present.
When the container is situated on the induction heater for heating
purposes, the temperature sensor and data element are in proximity
and the re-magnetization responses of the sensor can be detected
and used for temperature sensing.
This aspect of the invention is particularly advantageous because
the manufacturer of the heater can be assured that only consumable
items it also manufactures can be used with the heater; that is, if
the consumable item of another manufacturer is used with the
heater, no temperature monitoring can occur because that other
manufacturer's consumable item does not include the necessary
correlated magnetic field-responsive data element. In addition, the
heater can be designed so that it will not operate at all unless
the appropriate consumable item is used.
The invention also provides systems for heating of objects making
use of a temperature sensor in accordance with the invention. Such
systems further include apparatus for heating the object, such as
an induction or other type heating unit, along with a
re-magnetization response detector of the type described. A
controller coupled with the detector and heating apparatus is also
provided in order to receive output signals from the detector and
to control the operation of the heating apparatus in response to
such output signals. In these types of systems, the temperature of
the object is successively or continuously monitored, and the
controller vanes the operation of the heating apparatus so as to
heat the object or to maintain it in a desired temperature
range.
In another aspect of the invention, a temperature sensor as
described above is incorporated into an adhesive "sticker" that can
be quickly and easily adhered to a piece of servingware such as a
plate, dish, pan, glass, etc. As used herein, "adhesive" refers to
any composition or structure capable of providing the degree of
adherence required for attaching the temperature sensor to desired
servingware, including without limitation traditional adhesives or
"glues," as well as mechanical connection structure such as
Velcro.RTM. multiple hook and loop material or other fasteners.
Once such a temperature sensor is adhered to a piece of
servingware, the servingware may be placed on or in the vicinity of
an induction beater, heat lamp assembly, steam heating writ,
microwave oven, or other type heating unit equipped with a
re-magnetization response detector as described above or other type
of detector. The detector interrogates the temperature sensor to
sense the presence of the servingware, the type of servingware, and
the desired temperature or temperature range of the servingware. A
controller coupled with the detector and heating unit receives
signals from the detector which are indicative of the temperature,
or temperature range, of the servingware and which are used to
control the cycling or other operational parameter of the heating
unit. Thus, the temperature of the servingware may be continuously
or periodically monitored, and the heating unit may be controlled
so as to heat the servingware to a desired temperature range and to
maintain it within the temperature range.
The temperature sensor sticker described above may be formed by
adhering a microwire sensor or a plurality of such microwire
sensors to a substrate with an adhesive and then placing a release
layer over the exposed face of the adhesive. The adhesive secures
the microwire sensor or sensors to the substrate and, when the
release layer is removed, adheres the entire temperature sensor
sticker to a piece of servingware so that the servingware (and food
placed thereon) may be monitored and heated as described above.
Advantageously, the temperature sensors of the invention can be
quickly and easily adhesively attached to any existing servingware
without making any aesthetic or structural changes to the
servingware. Thus, the present invention allows temperature sensors
to be quickly and easily attached to servingware so as to allow
monitoring of a temperature parameter related to the servingware,
for example the temperature of the servingware, a desired
temperature of the servingware, a temperature range of the
servingware, a desired temperature range of the servingware, a
minimum temperature of the servingware, a maximum temperature of
the servingware, a heating property of the servingware, and the
temperature of a food supported on the servingware. Additionally,
the sensor may be used to wirelessly control such a temperature
parameter at any location during serving--such as at a wait
counter, serving table, buffet counter, microwave oven, or other
dining area location.
The temperature sensors can also be used with various types of
energy sources (halogen, induction heating, steam, microwave, etc.)
to heat the servingware using a temperature feedback, closed-loop
control method. The temperature sensors permit temperature
regulation of servingware wirelessly and indefinitely so that the
servingware is automatically heated to and maintained at a preset
temperature for as long as the servingware is positioned on or near
a heating unit.
The present invention accomplishes the above while being
inexpensive to implement and with few or no changes to normal
restaurant operational procedures.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a fragmentary view in partial section illustrating a
prior art magnetic microwire element suitable for use in the
present invention;
FIG. 2 is a graphical illustration of the magnetic characteristics
of a microwire suitable for use in the present invention, at
temperatures below the Curie temperature of the microwire
alloy;
FIG. 3A is a graph of time versus re-magnetization of an amorphous
strip typically used in conventional in anti-shoplifting EAS
markers or tags;
FIG. 3B is a graph of time versus re-magnetization of an amorphous
microwire having a large Barkhausen discontinuity, used in the
markers or tag commercially available from Sensormatic Co.;
FIG. 3C is a graph of time versus re-magnetization of a
glass-coated amorphous magnetic microwire produced by the Taylor
method;
FIG. 4 is an essentially schematic cross-sectional view of a
magnetic temperature sensor attached to an object to be sensed and
in accordance with a first embodiment of the invention;
FIG. 4A is an essentially schematic cross-sectional view similar to
that of FIG. 4, but illustrating the components of a magnetic
microwire temperature sensor split between two objects designed for
placement in proximity to each other;
FIG. 5 is a schematic cross-sectional view of a temperature-sensing
element in accordance with a second embodiment of the invention,
depicting a glass-coated amorphous microwire magnetic element
surround by a cylindrical sheath of a ferromagnetic metal or
ferrite material and having a desired Curie temperature;
FIG. 6 is an essentially schematic cross-sectional view of a
magnetic temperature sensor in accordance with the invention,
making use of microwire data elements of the type illustrated in
FIG. 1 and temperature-sensing elements as illustrated in FIG.
5;
FIG. 7 is a schematic cross-sectional view of another temperature
sensing element in accordance with a third embodiment of the
invention, wherein glass-coated microwire magnetic elements as
illustrate in FIG. 1 and located adjacent a shield of ferromagnetic
metal or ferrite material having a desired Curie temperature;
FIG. 8 is an essentially schematic cross-sectional view of a
magnetic element temperature sensor in accordance with the third
embodiment of the invention including data elements as illustrated
in FIG. 1 and temperature-sensing elements as illustrated in FIG.
7
FIG. 9 is a graph illustrating the Curie temperature versus
percentage of copper for nickel-copper alloys suitable for use as
sheaths for the temperature-sensing elements of the second
embodiment of the invention, or as shields for the
temperature-sensing elements of the third embodiment of the
invention;
FIG. 10 is a schematic block diagram of a temperature
reader/detector in accordance with the invention operable to
interact with the magnetic element temperature sensors hereof;
and
FIG. 11 is a schematic diagram illustrating magnetic element
sensor-based, closed-feedback temperature control induction heating
unit in accordance with the invention.
FIG. 12 is a perspective view of the bottom of a piece of
servingware shown with a temperature sensor constructed in
accordance with an embodiment of the invention attached
thereto.
FIG. 13 is a perspective view of the temperature sensor of FIG. 12
before it has been applied to the servingware and before its
adhesive release layer has been removed.
FIG. 14 is a perspective view of the temperature sensor of FIG. 13
after the adhesive release layer has been removed.
FIG. 15 is a vertical cross sectional view of the temperature
sensor of FIG. 13.
FIG. 16 is a schematic diagram in partial section illustrating a
piece of servingware with a temperature sensor adhered thereto
being heated by a flat-surfaced halogen heater.
FIG. 17 is a schematic diagram in partial section illustrating a
piece of servingware with a temperature sensor adhered thereto
being heated by a heat lamp heating unit.
FIG. 18 is a schematic diagram in partial section illustrating a
piece of servingware having an induction heatable grid and shown
with a temperature sensor adhered thereto being heated by an
induction heater.
FIG. 19 is a side view of the servingware shown in FIG. 18
illustrating the induction beatable grid on the servingware.
FIG. 20 is a schematic diagram in partial section illustrating a
piece of servingware with a temperature sensor adhered thereto
being heated by a steam table heating unit.
FIG. 21 is a side view of the servingware shown in FIG. 20.
FIG. 22 is a schematic diagram in partial section illustrating a
piece of servingware with a temperature sensor adhered thereto
being heated by a microwave heating unit.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Prior Art Magnetic Elements and Detection Systems
In order to best understand the present invention, it is helpful to
understand the nature and operation of present-day EAS and
authentication systems employing magnetic elements (often referred
to as "magnetic markers") and their corresponding detection
systems.
One type of magnetic element often used is a glass-coated amorphous
microwire. Such microwires, their production, magnetic properties,
and behaviors below their Curie temperatures, have been disclosed
in the technical and patent literature. See, for example, U.S. Pat.
Nos. 6,441,737 and 6,747,559; Horia Chirac, Preparation and
Characterization of Glass Covered Magnetic Wires, Materials Science
and Engineering A304-306, 166-71 (2001); Donald et al., The
Preparation, Properties and Applications of Some Glass Coated Metal
Filaments Prepared by the Taylor-Wire Process, Journal of Materials
Science, 31, 1139-48 (1996); Wiesner and Schneider, Magnetic
Properties of Amorphous Fe--P Alloys Containing Ga, Ge, and As,
Phys. Stat. Sol. (a) 26, 71 (1974); and Antonenko et al, High
Frequency Properties of Glass-Coated Microwires, Journal of Applied
Physics, vol. 83, 6587-89. Continuous lengths of microwires have
been produced inexpensively by what is generally called in the art
the Taylor process whereby either a pre-alloyed ingot or the
required elemental constituents are melted in a generally
vertically disposed glass tube that is sealed at the bottom. Once
the alloy is converted to a molten state, using radio frequency
("rf") heating for example, the softened bottom of the glass tube
is grasped and drawn into continuous microwire. Rapid reduction of
alloy cross-section, together with use of secondary cooling means,
cause the alloy to become amorphous or nanocrystalline during
drawing.
A typical microwire 20, anywhere from ten or less microns in total
diameter to tens of microns in total diameter, is depicted in FIG.
1. The wire 20 has an alloy core 22, and glass coating 24, wherein
the alloy core 22 and the glass coating 24 can be physically
coupled to each other continuously or only at several spatially
separated points. The glass-to-metal ratio, though variable, can be
tightly controlled. For example, the typical thickness of
glass-coating 24 may be from about 1-5 microns for a 45-60 micron
core diameter microwire, and typically 1-3 microns for 30 micron
core diameter microwire. Microwire elements for prior art EAS and
authentication tags are usually cut to lengths ranging from 15 mm
to 75 mm.
The microwire magnetic properties and resultant hysteresis loops
can be controlled by varying the alloy composition and the
glass-to-metal diameter ratio. FIG. 2 illustrates an idealized
magnetic hysteresis loop response of a typical microwire 20 with a
large Barkhausen discontinuity, suitable for use in the present
invention as described below. When such a microwire 20 is exposed
to an external alternating magnetic field whose field strength, in
the direction opposing the instantaneous magnetic polarization of
the element is greater than the coercive force H.sub.c, here shown
ideally to be less than 10 A/m, the re-magnetization process
results in the generation of a harmonically rich pulse that is
easily detected. The magnetic flux changes during the pulse give
rise to a peak in the flux derivative over time. Accordingly, a
voltage peak will be observed in a receiving coil placed in the
vicinity of the element and the reader/detector may correlate that
voltage peak to the presence of a microwire element in the
field.
Prior art glass-coated amorphous microwires 20 produced by the
Taylor method can be fabricated so as to exhibit very low
coercivities (substantially less than 10 A/m), high relative
permeabilities (substantially higher than 20000), substantially
zero or slightly positive magnetostrictions, and large Barkhausen
discontinuities (which means that the microwires exist essentially
only in bimodal magnetic states).
The re-magnetization properties of the microwires 20 are also
important, and distinguish such microwires from other types of
prior art magnetic elements. Referring to FIG. 3C (see U.S. Pat.
No. 6,556,139) it will be seen that the re-magnetization peak width
(measured at half amplitude level) was in the range of 25-80 micro
seconds for a glass-coated amorphous microwire. In contrast (see
FIG. 3B), markers or tags commercially available from Sensormatic
Co. comprises an in-water-cast amorphous wire with large Barkhausen
discontinuity, the peak width was in the range of about 200-500
micro seconds or more. Finally (see FIG. 3A), the peak width was
about 1-2 milliseconds for amorphous strips typically used in
anti-shoplifting markers or tags, e.g., a Meto GmbH 32-mm marker or
tag. Thus, microwires of the type illustrated in FIG. 1 exhibit
extremely short re-magnetization peaks which allow discrimination
of a microwire response from background noise such as that caused
by field interaction with other external objects.
Zhukov et al., J. Mater. Res. 15 No. 10 Oct. (2000), describe the
production of multi-bit markers when utilizing multiple amorphous
glass-coated wire segments, each having a different dimension
(length, gross diameter, etc.) or magnetic property (e.g., coercive
field). For instance, if a plurality of magnetic microwire elements
exhibit different coercivities, respectively, each of their unique
re-magnetization peaks can be detected in each magnetic field
period, and their pattern may be recognized, for example, by
methods described in U.S. Pat. No. 4,203,544. U.S. Pat. No.
5,729,201 describes a method to differentiate such a plurality of
wires, even if they have the same magnetic properties and
dimensions. A permanent magnet bias field element in the vicinity
of the wire serves to differentiate the amplitude of the external
magnetic field generated by a reader/detector that is required to
exceed the coercive force for re-magnetization of each magnetic
element by way of its different proximity to each individual wire
segment. This leads to a phase difference in re-magnetization peaks
detected, thus allowing differentiation of the individual
elements.
U.S. Pat. No. 4,134,538 describes multi-element tags (markers)
constructed of magnetic elements, each characterized by a different
coercive force and thereby permitting the assignment to any
attached object of a reference code with as many characters as
magnetic elements utilized. One thus assigns, respectively, each
character of the reference code to a magnetic element in the order
of the values of their respective coercive forces, the signals
corresponding to each magnetic element then appearing in the
detection apparatus in the same order of dephasing as the order of
the coercive forces and each with amplitudes corresponding to the
values assigned at the time of coding, thus reproducing the
complete code in arrangement and in amplitude.
U.S. Pat. No. 6,622,913 teaches that data information may be
encoded in binary form by using microwire elements of different
diameters or permeabilities, so that they produce considerably
different responses to an alternating magnetic field produced by a
transmitter. Accordingly, one type of microwire may present binary
"0" and the other binary "1". For instance, an array of four
microwires each with successively larger coercivities such that
they are each easily distinguished by their detected phase
differences over a period of an incident alternating magnetic
field, can be made to produce alternating high and low amplitudes
of field perturbations (and thus alternating high and low voltage
amplitudes at the detector) so that they represent a binary pattern
of 1010.
U.S. patent application No. 2005/0109435 describes several magnetic
and optical methods of encoding multi-bit information on a single
microwire. The stress sensitivity of ferromagnetic amorphous
glass-coated microwire can be used advantageously as the physical
basis for affecting magnetic domain structure. Ferromagnetic
amorphous glass-coated microwire encoding can result from a
localized alteration of this domain structure. The alteration is
readily accomplished by imposition of localized stresses or by
selective crystallization of the amorphous alloy. Such changes are
affected by a number of means, including localized heating via
pulsed laser, chemical thinning of the glass coating, coatings on
the glass, and the like. Localized modifications of the
glass-coating of ferromagnetic amorphous glass-coated microwires
can be used to effectively produce controlled changes in the
magnetic domain structure of the amorphous alloy cores, thereby
enabling encoding. The preferred method is to use laser pulses to
locally heat the glass or alloy (independent heating can be
accomplished by choice of wavelength) causing changes in the
structure of one or both, and thereby altering the extant stress
fields or the basic magnetic characteristics.
Prior art EAS or authentication system detector devices used in
conjunction with all types of magnetic elements used as magnetic
markers typically use field transmitter unit and a magnetic field
detector unit. The field transmitter generally has a frequency
generator and a field generator coil (constituting together an
alternating magnetic field source) for creating the alternating
magnetic field in the interrogation zone of the marker. The
detector unit normally has a field receiving coil and a signal
processing unit that typically triggers an alarm device.
In prior art EAS systems, when a magnetic marker is located in the
vicinity of the coils, the interrogating AC field causes the
switching of the magnetic element's magnetization. Accordingly,
very short pulses of magnetic field perturbations are received by
the field receiving coil. These pulses are detected by the signal
processing circuit, which produces an output to activate an
alarm.
First Embodiment: Modified Chemistry Microwires for Curie
Temperature Sensing
The first embodiment of the invention comprises a magnetic
mnicrowire temperature sensor having at least one and usually a
plurality of magnetically susceptible microwires, with the
individual alloys of at least certain of the microwires having
modified chemistries and consequent different Curie temperatures,
usually below about 400.degree. C. Additionally, this embodiment
includes a microwire reader/detector capable of decoding
temperature information derived from the sensor microwires.
Chemically modified individual microwires are preferably fabricated
so that the modified microwires retain large Barkhausen
discontinuities, extremely low coercivities, and extremely high
permeabilities below their respective Curie temperatures (with
resultant hysteresis behavior of the type depicted in FIG. 2).
These modified microwires essentially completely lose their
ferromagnetism above their Curie temperatures. Other microwires
within the any of the sensor need not have modified chemistries,
but can operate as data elements according to any of the prior art
methods of single or multi-bit encoding previously discussed.
The most preferred chemical modification of Fe-based and/or
Co-based alloys used in prior art amorphous microwires is the
adjustment of the atomic percentage of chromium therein. Chromium
in amorphous iron-based (Fe80-xCrx)(PC)20 alloys has a sizeable
effect on their magnetic properties. An increase in Chromium
percentage lowers the Curie temperatures, the average hyperfine
fields, and the saturation magnetizations thereof and on the other
hand markedly increases their initial permeabilities. For instance,
an increase in the Chromium percentage from 0% to 6.5% reduced the
Curie temperature from 330.degree. C. to 155.degree. C. in certain
tested samples. See, Henry et al., Magnetic Measurements of
Iron-Rich Amorphous Alloys Containing Chromium: Mossbauer Study and
B--H Loops, Journal of Materials Science 19:1000-06 (1984); and
Wijn, Magnetic Properties of Metals--d-Elements, Alloys, and
Compounds, Springer-Verlag, Berlin (1991).
Other chemical changes to Fe-based and Co-based alloys can also be
utilized to alter the magnetic characteristics of amorphous
microwire elements. For example, Co can be substituted for Fe in
certain FCZBN alloys, and the resultant Curie temperature exhibits
an sinusoid-like behavior with increasing Co content, and reveals
two maxima at 3 and 12.5 atomic % Co and a minimum at 7.5 atomic %
Co (Yao et al., Co Dependence of Curie Temperature in Amorphous Fe
Co Zr B Nb Alloys With High Glass Forming Ability, Journal of
Physical Science: Condensed Matter, Vol. 16 6325-34 (2004). IEEE
Transactions on Magnetics, Vol. 22, 1349-51 (1986) presents a
process whereby Co--P amorphous alloys with a high P content can be
electrolytically obtained. The Curie temperature of these alloys
shows a linear behavior in Curie temperature versus composition up
to 28-29% P. For higher concentrations, a constant Curie
temperature is observed.
As explained above, the first embodiment preferably makes use of a
plurality of magnetic microwire temperature sensing elements whose
chemistries have been changed so that the microwires become
paramagnetic at individual temperatures (usually about 400.degree.
C. or below) within specific design temperature range of the
overall temperature sensor. For example, FIG. 4 depicts a
temperature sensor 26 having a total of four temperature-sensing
microwires 28-34 forming an array 36. Each of the microwires 28-34
has its chemistry modified using any of the forgoing techniques
such as an increasing atomic percentage of chromium, with the
result that the Curie temperatures of the microwires are different
and are all exceeded during the normal operating temperature range
of the sensor 26. The remaining two microwires 38 and 40 are data
elements. An optional permanent magnetic bias field element 41 can
also be employed.
In the FIG. 4 embodiment, the microwires 28-34 are arranged in
parallel relationship where the spacing 42 is equal to the sum of
the radii of each adjacent microwire (spacing 42 may be larger than
the sum of the radii), and are held together by a thermally
conducting adhesive (not shown) that also adheres the microwires to
an object 44 to be temperature-monitored.
In this exemplary embodiment, the magnetic coercivity of each
microwire 28-34 and 38-40 is altered by appropriate chemical
changes in the alloys thereof, and specifically the chromium
content of each alloy, in order to ensure that each of the six
microwires is uniquely detectable within each period in the order
of their location within the overall array. Of course, other prior
art techniques for changing alloy chemistry as well as for
adjusting coercivity can also be used for this purpose.
Additionally, each of the six microwires 28-34 and 38-40 are of the
same length (e.g., 20 mm) except for microwire 38, which is
significantly longer (e.g., 40 mm). This extra length for the
microwire 38 ensures that the detected re-magnetization peak from
this data element microwire is larger in amplitude than all other
re-magnetization peaks.
FIG. 10 illustrates an exemplary detector device 46 used to detect
temperatures sensed by sensor 26, corresponding to the temperature
of the object 44. The detector 46 broadly includes an alternating
magnetic field transmitter unit in the form of a frequency
generator 48 coupled with a field generator coil 50, such that the
transmitter unit is operable to create an alternating magnetic
field for interrogating sensor 26. The overall device 46 further
includes a field receiving coil 52 operably coupled with a digital
signal processing unit 54 and a temperature display 56. As
illustrated, the processing unit 54 is equipped with communication
ports 58 and 60, and may be operably coupled with frequency
generator 48 via connection 62. Additionally, frequency generator
48 may be equipped with an optional input 61 permitting remote
control of the generator.
The signal processing unit 54 operates using a decoding algorithm
having the capability to decode the magnetic field perturbation
information received upon interrogation of the sensor 26.
Preferably the decoding algorithm is in the form of one or more
look-up tables for different sensors in accordance with the
invention, stored within memory associated with the unit 54. In the
case of a detector 46 specific to sensor 26, the temperature
look-up table would have both the expected phase position (phase
relationship from the stop bit and/or from each other) for each of
the four temperature sensing microwire elements 28-34, as well as
the temperatures to report for each of the acceptable detected bit
codes from the array 36 of microwires 20 (some bit codes may be
unacceptable because they make no logical sense according to the
phased microwire order of Curie temperatures and thus are the
product of a mis-read by detector 46).
As described, the sensor 26 and detector device 46 are correlated
so that the device 46 can, by proper interrogation of sensor 26,
ascertain the temperature of object 44. Such correlation involves
matching the bit logic of sensor 26 with the decoding algorithm(s),
in this case, the temperature look-up table(s) stored in the memory
of signal processing unit 54. Those skilled in the art will
appreciate that a wide variety of bit logics and corresponding
algorithms tables can be provided. However, the following
discussion provides one exemplary system in the context of the
sensor 26 and detector device 46 of FIG. 10.
Again referring to FIG. 4, assume that the least significant bit of
the four temperature-sensing element microwires 34-38 is microwire
28, which can be denominated the "first" microwire. Thus, when
object 44 is below the Curie temperature of the first microwire 28,
the microwire 28 will still produce its characteristic short
re-magnetization pulse under the influence of the alternating
magnetic field generated by device 46. When object 44 has a
temperature above the Curie temperature of the first microwire 28,
the microwire 28 will no longer produce its short re-magnetization
pulse under the influence of the applied alternating magnetic
field, and therefore its bit will be missing (a "0" value) from the
detected temperature-sensing element array of bits.
The remaining temperature-sensing microwires 30-34 each have
respective, chemically modified alloys therein, so that the Curie
temperatures of the microwires are successively and in stepwise
fashion slightly higher than that of the first microwire 28. Thus,
the "second" microwire 30 has a slightly higher Curie temperature
than the first microwire 28, and the "third" and "fourth"
microwires 32 and 34 each have successive, slightly higher Curie
temperatures than the lower-order microwires. In this manner the
re-magnetization pulses (bits) of the microwires 30-34 will
disappear (i.e., become a "0" value) under the influence of the
applied magnetic field from detector 46 at respective temperatures
each higher than that of the first microwire 28 and of all
preceding lower-order microwires.
For example, if the object 44 has a temperature below the Curie
temperatures of both the first and second microwires 28 and 30, all
bits of the array 36 will be read (i.e., become a "1" value) by the
device 46. If the object 44 has a temperature above the Curie
temperature of first microwire 28, but below the Curie temperature
of second microwire 30, the first bit will have disappeared to the
device 46 as a "0" value, and the remaining bits corresponding to
microwires 30-34 will be read as a "1" value by the device 46.
As noted above, the device 46 contains algorithm(s) in the form of
look-up table(s) that recognize that the disappearance of the first
temperature bit and the appearance of the second and all higher
temperature bits means that the temperature of object 44 exists
somewhere between the first and second Curie temperatures of the
first and second microwires (temperature bits) 28 and 30 (as used
herein, detection or determination of sensor or object temperature
can refer to a single temperature or an approximated temperature
within a range of temperatures). Thus, by reading the
temperature-sensing bit data generated by the array 36, and
correlating the binary value of this data to the look-up table of
interest, the temperature of object 44 can be determined within the
temperature range defined by the interval between the first and
second microwire Curie temperatures. Of course, this logic applies
to all four of the microwires 28-34, of the simple FIG. 4
example.
If the number N of temperature-sensing microwires on a given
magnetic element temperature sensor have identified Curie
temperatures of known increasing sequential order, and these Curie
temperatures are selected to be at least somewhat consistent in
their increments from one to another, the sensor can detect
temperatures from the first to the N.sup.th Curie temperatures. The
resolution of such a sensor is the increment between sequential
Curie temperatures. It will be appreciated that even if the
sequential Curie temperatures are not exactly consistent, the
relevant look-up table can be constructed and the sensor can
properly function.
The microwire alloys of this embodiment can have their Curie
temperatures quantified before or after the alloys have been
processed into microwires. In this fashion the complete microwire
sensor can be calibrated for temperature sensing. For a given
temperature range to be measured, the greater the number of
microwires whose Curie temperatures are quantified and are
near-equally spaced within the temperature range, the higher the
resolution of the microwire temperature sensor. Preferably,
temperature sensors in accordance with this embodiment have at
least 20 temperature-sensing microwires, each having sequentially
higher Curie temperatures, with first to N.sup.th microwires and
with no more than a 5.degree. C. increment between successive
microwires.
In cases where a certain temperature-sensing microwire does not
disappear in proper sequence with the other microwires (due to a
misread by the reader/detector, a lack of thermal contact with the
others, or other reason), the lack of an acceptable look-up table
value preferably causes the reader/detector algorithm of device 46
to attempt a re-read of the sensor 26. If continuous re-reads show
the same anomalous temperature data, the reader/detector algorithm
can discard the temperature data, use the last measured temperature
(or the last measured temperature plus a delta temperature that is
based upon a calculation involving the last measured rate of change
of temperature and reading time interval), and then try again at
the next scheduled read interval. Preferably, steps are taken to
ensure that all microwires make good thermal contact with each
other and the object 44 whose temperature is to be measured. One
such step is to attach all of the microwires to a thin, thermally
conductive substrate. Another step is to employ thermally
conductive encasing or potting materials as described
hereinafter.
It is known that up to 40 microwires may be detected within a
period, and accordingly a magnetic element temperature sensor of
this embodiment may contain many more than four temperature-sensing
microwires 20 and many more than one (not counting the stop bit)
data elements. Data elements, especially if each is encoded with
multi-bit data, can be used to store correlation information (such
as linear or non-linear relationship constants) that can allow the
detector algorithm to decode the "specific numerical value"
(temperature bits) to its associated temperature value. This is
particularly valuable where a look-up table method is not used.
Thus, the magnetic element temperature sensor 26 may store in its
data elements data such as a permanent ID code or a "class of
object" code. This ability to store a "class of object" code allows
a single reader/detector algorithm to read several different types
of microwire temperature sensors, each with its own unique look-up
table, and still decode the correct temperature.
It will be appreciated that a number of different encoding/decoding
strategies can be employed in sensor 26 and device 46 without
departing from the scope of the present invention, providing that
each temperature-sensing microwire is designed to lose its
re-magnetization pulse properties under the influence of the
alternating magnetic field generated by device 46 above its Curie
temperature. One option would be the use of bias field element 41,
which serves to differentiate the amplitude of the external
magnetic field generated by device 46 that is required to exceed
the coercive force for re-magnetization of each microwire, owing to
its different proximity to each individual microwire 28-34 and
38-40. This leads to a phase difference in re-magnetization peaks
detected by detector 46, thus facilitating differentiation of the
six individual microwires. Other variations would include without
limitation means to determine a stop or "delineation" bit between
temperature-sensing elements and data elements, encoding and
decoding of non-temperature data, and differing lengths for some or
all of the microwires in order to alter the magnetic responses
thereof. Additionally, changes in magnetic properties at
temperatures close to the Curie temperatures of the individual
temperature-sensing microwires can alter but not entirely eliminate
the detectable re-magnetization pulses thereof. Such altered
re-magnetization pulses, having predictable behaviors over specific
temperature ranges below the Curie temperatures, may also be used
to decode temperature information. This can allow each
temperature-sensing microwire to accurately sense more than one
temperature, e.g., from a small interval below the Curie
temperature up until the Curie temperature.
Second Embodiment: Microwires with Ferromagnetic Sheaths for
Temperature Sensing
This second embodiment comprises a magnetic element temperature
sensor 64 having a plurality of composite temperature-sensing
microwires 66 each including a magnetically susceptible microwire
of the prior art type described above that has no intentional
reduction of its Curie temperature, such that it will retain its
large Barkhausen discontinuity and other magnetic properties as
depicted in FIG. 2 throughout the entire operating range of the
sensor 64. This microwire structure further includes a surrounding,
tubular, structure 68. The overall second embodiment further
includes a microwire temperature detector similar to detector 46
having stored algorithm(s) capable of decoding the temperature
information derived from interrogation of the sensor 64.
In particular, each of the composite microwires 66 has an innermost
alloy 70 surrounded by an intermediate glass coating 72, such that
this inner portions of the composite microwires 66 are conceptually
identical with previously described prior art microwires 20.
Additionally, the structure 68 of the microwires 66 include a
tubular sheath 74 of ferromagnetic metal or Ferrite material (such
as NiZn or MnZn) surrounding the coating 72, and an optional
outermost glass coating 76 surrounding the tubular sheath 74. The
sheath 74 has a Curie temperature carefully chosen so that the
individual, inner microwire alloy 70 will produce its signature
perturbations (and thus re-magnetization voltage pulses at the
detector) only when the microwire is placed in the alternating
magnetic field generated by the detector, and then only above the
Curie temperature (or above some temperature near the Curie
temperature) of the ferromagnetic sheath 74. Hence, when the
composite microwire 66 experiences a temperature below the Curie
temperature of the ferromagnetic sheath 74 (or below some
temperature near this Curie temperature), the sheath 74 is
ferromagnetic, thus altering the signature pulse of the microwire
66. This may prevent re-magnetization of the composite microwire 66
owing to magnetic saturation caused by the sheath 74, or may allow
the resulting re-magnetization as a biased or "altered" signal from
the composite microwire 66. For example, the re-magnetization pulse
may be offset in phase from its location above the sheath Curie
temperature, or the biasing effect of the sheath may allow altered
re-magnetization responses below and above a plurality of different
set point temperatures.
When the composite microwire 66 experiences a temperature above the
Curie temperature of the sheath 74, the sheath becomes paramagnetic
and thus has no effect upon the signature pulse of the alloy 70.
Therefore, above the individual Curie temperatures of the sheaths
74 (or above some temperatures near these Curie temperatures), the
composite microwires 66 act normally (i.e., they cause the detector
46 to detect a voltage pulse as expected in phase, amplitude or the
like, as recorded in a look-up table or via some other decoding
algorithm). However, when the composite microwires 66 experience
temperatures below the individual Curie temperatures of their
sheaths 74, they are either not detectable by the detector, or are
detectable but have their magnetic properties altered, especially
in relation to signature pulses detected above temperatures of the
Curie temperatures of their sheaths 74. Such altered magnetic
properties would not fit the parameters of the look-up table or
other decoding algorithm, such as phase relationship to an
alternating current from the frequency generator 48, or pulse
duration.
If the material making up tubular sheath 74 is a ferronmagnetic
metal, the sheath 74 may be only microns thick or as thick as
required for saturation for inner microwire alloy 70, and for
manufacturability. One method of forming the ferromagnetic sheath
74 is described in U.S. Pat. No. 7,011,911 entitled "Amorphous
Microwire and Method for Manufacture Thereof." Other methods
include flame spraying or sputtering. When using these methods for
creating the sheath 74, it is not necessary that there be an
outermost coating 76. A modified Taylor method may also be
employed, wherein an inside glass tube and an outside glass tube
are coaxially and telescopically aligned such that the inside glass
tube resides within the walls of the outside glass tube. The alloy
70 is inside the center glass tube in ingot (rod-shaped) or
constituent metal form, whereas the material making up tubular
sheath 74 is located between the interfitted glass tubes. This
sheath material may be in ingot (possibly several rods) or
constituent metal form. The alloys are heated to molten by magnetic
induction or other suitable means and the resultant molten metal
and glass is quickly drawn to form a composite microwire 66.
Techniques are known in the art for adjusting the Curie
temperatures of ferromagnetic alloys by addition of trace elements
of specific metals. Thus, any number of alloys may be used to make
up the tubular sheaths 74. FIG. 9 illustrates that small additions
of certain metals (in this case Copper) to ferromagnetic metal
elements (in this case Nickel) so as to form a true alloys can
alter the Curie temperature of the resultant ferromagnetic alloys
in a predictable way. Also, additions of small amounts of Chromium
to Iron yield alloys whose Curie temperatures are predictable. See
U.S. Pat. No. 5,954,984, for a discussion on modifying the Curie
temperature of Nickel with Copper and Aluminum.
The alloys or Ferrite materials used in the fabrication of the
tubular sheaths 74 can have their Curie temperatures (or regulation
temperatures near their Curie temperatures) quantified before or
after the alloys or Ferrite materials have been processed into
tubular sheaths 74. Thus, the magnetic element temperature detector
46 can be readily calibrated for temperature sensing. As before,
for a given temperature range to be measured, the more
temperature-sensing composite microwires 66 whose sheath Curie
temperatures are quantified and are near-equally spaced within the
temperature range, the higher the resolution of the temperature
sensor. It is preferred to have at least 20 temperature-sensing
composite microwires 66, each having a sequentially higher sheath
Curie temperature, at most 5.degree. C. above the next lowest order
sheath. Of course, if the sheath 74 alters the re-magnetization
pulse of the microwire 66 over a range of temperatures near the
Curie temperature of the sheath 74 (say, for instance, by
detectably shifting the phase of the re-magnetization pulse), it
may be possible for the detector to sense and decode multiple
temperatures for each microwire 66 within a certain range, thus
requiring fewer microwires 66 to allow a sensor to accurately
measure temperatures over a wide range.
If the material making up the tubular sheaths 74 is a Ferrite or
some blend of materials with Ferrite, then the sheath may either be
adhered to the glass layer 72, a separate cylindrical bead, or
other sintered Ferrite cylindrical object with a central hole such
that the alloy 70 and surrounding glass 72 may be placed therein.
Alternately, the tubular sheath 74 could be formed as a part of the
glass layer 72 by using a glass-ferrite material for layer 72 in
lieu of pure glass. U.S. Pat. No. 6,909,395 entitled "Radar
Absorbing Coatings" describes Ferrite/glass composite material that
can be used to either adhere directly to a metal wire or other
shape of metal object, or can be adhered to a layer of pure glass
that is already adhered to the metal.
Referring now to FIG. 6, the sensor 64 includes a plurality of
microwires 20 presenting an array 78 of data elements, and a
plurality of temperature-sensing composite microwires 66 forming an
array 80 thereof. The microwires 20 and composite microwires 66 are
attached to a sensor or tag substrate 82, which is as thin and as
thermally conductive as possible so that the sensor 64 may be
placed in intimate thermal contact with an object (not shown) for
temperature measurement purposes.
The microwires 20 making up array 78 have chemistries giving
individual Curie temperatures above the planned operating
temperature range usually less than about 400.degree. C. for the
sensor 64. The composite microwires 66 within array 80 are
preferably spaced apart by a distance 84, such that the
ferromagnetic or Ferrite tubular sheath 74 of each individual
composite microwire 66 does not affect its neighbor composite
microwire once the tubular sheath 74 of the individual microwire
experiences a temperature above its Curie temperature.
In this simple embodiment, assume that each data element of array
78 is laser coded to a logic state of "1" or "0." Furthermore,
assume that each of the data elements is the same length (say, 20
mm) except for terminal elements 83 and 86, which are significantly
longer (say 40 mm). This extra length ensures that the detected
re-magnetization peaks from data elements 83 and 86 are larger in
amplitude than the others. Finally, assume that the data element 83
is laser coded to a logical "1" value whereas data element 86 is
laser coded to a logical "0" value. As described in the first
embodiment, each of the elements of both arrays 78 and 80 are made
so that the detected phase order matches the depicted alignment
order from top (microwire 83) to bottom (composite microwire 88),
the latter having the highest sheath Curie temperature of the
composite microwires of the array 80. hi such case, the detector 46
assigns the first detected pulse (in phase relationship) with the
highest amplitude with a logic level "1" as the start bit (here
depicted as microwire 83) and the last detected data microwire 86
with highest amplitude and with a logic level "0" as the stop bit.
All data microwires between the start and stop bits 83 and 86 are
detected by the microwire temperature reader/detector as data bits.
The intervening data microwires can be used, as described in the
first embodiment, for a variety of functions such as tag
identification number and "class of object" code.
In order to decode the temperature information from sensor 64,
assume there are "N" composite microwires from the array 80 that
have ferromagnetic sheaths 74 such that all of the respective
sheaths 74 have Curie temperatures which are exceeded (or have
regulation temperatures "near" the Curie temperatures) during the
normal operating range of the sensor 64. The least significant bit
of these N composite microwares 66, detected in phase relationship
just after the stop bit 86, and at a specified phase relationship
from the stop bit 86, is deemed the "first" composite microwire 89.
Thus, the first composite microwire 89 will begin producing its
normal short pulse perturbation only at temperatures above the
Curie temperature of its sheath 74, and hence the detector 46 will
only then detect its voltage pulse (bit). The first composite
microwire 89 will not produce its normal short pulse perturbation
below the Curie temperature of its sheath 74, and therefore its bit
will either be missing from the bits detected by detector 46, or
its pulse will be so altered as to be clearly detectable by the
detector 46 as an "altered" microwire.
A "second" composite microwire 90 in phase relationship from the
stop bit 86 (the next-to-least significant bit) has a ferromagnetic
sheath 74 of slightly higher Curie temperature than that of the
first composite microwire 89. The bit of composite microwire 90
will not be read by the detector 46 or its voltage signal will be
detected as "altered" at temperatures below this higher sheath
Curie temperature (or higher temperature near the sheath Curie
temperature), but will appear as expected in phase and duration at
a higher temperature than that of the first composite microwire
89.
Thus, if the sensor 64 is subjected to a temperature below that of
the Curie temperatures (or designated temperatures below the Curie
temperatures) of both the first and second composite microwires 89
and 90, no composite microwires will be detected by the detector 46
(assuming that all subsequent higher order composite microwires in
array 80 have sheaths 74 with a higher Curie temperature). If the
sensor 64 is subjected to a temperature above the sheath Curie
temperature (or related temperature) of the first composite
microwire 89 but below the sheath Curie temperature (or related
temperature) of the second composite microwire 90, the first bit
will be read by the detector 46 but the second bit will either
still not be read by the detector 46 or will have an "altered"
signal as read by the detector. Finally, if the sensor 64 is
subjected to a temperature higher than the sheath Curie temperature
(or related temperature) of both the first and second composite
microwires 89 and 90, both the first and second composite
microwires will be read by the detector 46.
The detector 46 contains a decoding algorithm that recognizes that
the appearance of the first temperature bit of first composite
microwire 89, but the lack (or alteration of) of the second
temperature bit of second composite microwire 90, and thus signals
via display 56, that the sensor temperature exists somewhere
between the first sheath Curie temperature and the second sheath
Curie temperature. Thus, if the sensor 64 is placed in intimate
thermal contact with an object whose temperature is of interest,
then by reading the composite microwire array bit output of the
sensor 64, the detector 46 determines the object's temperature
within the temperature range defined by the interval between the
first and second sheath Curie temperatures (or between their
respective temperature near their Curie temperatures).
If the number of composite microwires 66 on the sensor 64 have
sheath Curie temperatures known to be in increasing sequential
order is increased to "N" composite microwires, and these sheath
Curie temperatures are selected to be at least somewhat consistent
in their increments from one another, the sensor 64 has detectable
temperature range from the first to the N.sup.th sheath Curie
temperatures, and has a temperature resolution defined by the
increment between sequential sheath Curie temperatures.
More generally, the detector 46 decoding algorithm is built to
understand that the appearance of the first through the N-1.sup.th
temperature bits generated by the corresponding composite
microwires 66 in their normal pulse state, together with the lack
of the N.sup.th temperature bit corresponding to N.sup.th composite
microwire 66 in its normal pulse state, establishes that the sensor
temperature exists somewhere between the N-1.sup.th sheath Curie
temperature and the N.sup.th sheath Curie temperature (or between
their respective temperatures near the sheath Curie temperatures).
The detector algorithm preferably reports this sensor temperature
to be the midway temperature between N-1.sup.th and N.sup.th Curie
temperatures.
Preferably, the acceptable composite microwire bit patterns and
their corresponding sensor temperatures are stored in a look-up
table within the memory of detector 46. Thus, when an acceptable
bit pattern is detected by detector 46 from a correlated sensor 64,
this pattern is compared against the look-up table to find the
correlating sensor temperature.
In cases where one or more composite microwires 66 of array 80 do
not appear in their normal state in proper sequence with the others
(due to a mis-read by the detector 46, a lack of thermal contact
with the other composite microwires, or some other reason), the
detector algorithm preferably attempts a re-read of the sensor 64.
If continuous re-reads show the same anomalous bit pattern, the
detector algorithm can discard the temperature data, use the last
measured temperature (or the last measured temperature plus a delta
temperature that is based upon a calculation involving the last
measured rate of change of temperature and reading time interval),
and then try again at the next scheduled read interval.
Third Embodiment: Microwires with Separate but Adjacent
Ferromagnetic Saturation Elements for Temperature Sensing
The third embodiment is conceptually very similar to the second
embodiment and differs in the use of ferromagnetic sheath
saturation or biasing elements as separate entities which do not
need to touch the surface of the adjacent temperature-sensing
microwires, as compared with the sheaths 74 of the second
embodiment which are bonded or otherwise affixed to central
microwire structure. Referring to FIG. 7, a combination microwire
92 is illustrated and includes a microwire 20 of the type
previously described that has no intentional reduction of its Curie
temperature, such that it will retain its large Barkhausen
discontinuity and other magnetic properties as depicted in FIG. 2
throughout the entire operating range of the sensor. Also, the
combination microwire 92 includes an adjacent ferromagnetic sheath
94. The sheath 94 is located near enough to the associated
microwire 20 so as to prevent by magnetic saturation or biasing
re-magnetization of the microwire 20 and consequent generation of
its signature perturbation until the combination microwire 92
experiences a temperature above the Curie temperature (or above
some temperature near the Curie temperature) of the sheath 94.
Again, as in the case of the second embodiment, the sheath 94 can
be designed so that the associated microwire 20 will exhibit a
series of different re-magnetization responses below and above
different set point temperatures below the sheath Curie
temperature, and if desired such multiple different responses can
be used for temperature sensing and determination.
In more detail, the sheath 94 is preferably in the form of a thin
rectangular sheet of ferromagnetic metal whose size is not
significantly wider than that of the associated microwire 20, and
whose flat surface may be bent into a half-round shape (or, in the
case Ferrite, may be sintered into a half-round or some other
suitable shape). The Curie temperature of the shield 94 is
carefully chosen so that the associated microwire 20 will produce
its signal perturbation (and thus a re-magnetization pulse of
voltage) when the combination microwire 92 is placed in an
alternating magnetic field of the detector 46 and only when the
combination microwire 92 experiences a temperature above the Curie
temperature (or above some fixed temperature near the Curie
temperature) of the sheath 94. The sheaths 94 need only be microns
thick or as thick as needed for saturation of the associated
microwire 20, and for ease of manufacturing. The same types of
alloys or Ferrites described in connection with the second
embodiment may be used in the fabrication of sheath 94.
Furthermore, magnetic inks (using either ferromagnetic powder or
Ferrite powder) arc also suitable and have the advantage of being
printable on a supporting substrate for the combination microwires
92.
Referring to FIG. 8, a temperature sensor 96 is illustrated, which
is in all respects identical with sensor 64, save for the use of
combination microwires 92 in lieu of the composite microwires 66.
Accordingly, like reference numerals from FIG. 6 are used in FIG. 8
to denote identical components, and an "a" designation has been
used to distinguish the combination microwires 92 from the
composite microwires 66.
The operation of sensor 96 is identical to that of sensor 64, and
makes use of a similar detector 46 having appropriate decoding
algorithms (preferably look-up tables) correlated with the sensor
96. Accordingly, a detailed description of this operation is
unnecessary.
The above-described three embodiments, and indeed other embodiments
within the scope of the present invention, can be varied in a
number of different respects. For example, FIG. 4A depicts an
alternative arrangement advantageous for some product applications.
Specifically, in FIG. 4A a sensor 26a is provided wherein the
microwire data element 40 is attached to a first object 44a,
whereas the remaining data microwire 38 and the temperature-sensing
microwires 28-34, and optional bias element 41, are attached to a
second object 44b. The bit logic of sensor 26a is identical with
that of sensor 26, meaning that, even though the components of the
sensor 26a are separated onto objects 44a and 44b, the overall
sensor 26a will only operate when all of the sensor components are
within the alternating magnetic field generated by detector 46. If
this condition does not exist, then no successful reading using the
detector 46 can occur. This construction can be used, for example,
to control heating of a two-part object by a heater only if the
heater's detector detects both part of the sensor (and thus both
objects 44a and 44b), and to correspondingly prevent any heating
unless both parts of the sensor are present and within the magnetic
field of detector 46. In such a case the heater control would
typically be coupled with the signal processing unit 54 of detector
46.
Of course, this same design concept maybe used when more than two
objects are present. Additionally, more sophisticated data encoding
methods such as those described above may be used to correlate one
or more pieces of the overall sensor 26a with matching pieces
thereof. Such methods may include laser encoding the first data
element 40, with a matching multi-bit code for stop data bit
38.
Although the FIG. 4A alternative has been described with reference
to sensor 26 of the first embodiment, it will be appreciated that
the same modification may be used with sensors 64 and 96 of the
second and third embodiments if desired.
The microwires forming a part of the sensors 64 and 96, just as in
the case of the microwires 20 of sensor 26, may be bound onto an
object 44 or a thermally conductive substrate such as substrate 82
using an appropriate adhesive. In another alternative, the
microwires 20, composite microwires 66 and/or combination
microwires 92 may be encased in very thin, non-ferromagnetic,
thermally conductive material such as a graphite-filled polymer
material that is compression or injection moldable, such as one
within the family of materials sold by SGL Carbon under the
designation RIDURID.RTM.. Other useable high-temperature materials
include ceramic potting materials sold by Aremco under the
designation Ceramamcast 510, or other flexible high-temperature
polymers. With use of such materials the thickness and overall
thermal mass of the encasing material should be kept to a minimum
in order to minimize thermal lag between the object to be
temperature monitored and the core alloy materials of the
microwires.
Additionally, the microwires of the described embodiments may be
twisted into a thread or woven into the structure of an object to
be temperature-monitored if appropriate. For instance, the
microwires may be woven into a carbon fabric cloth, so long as good
thermal contact can be maintained and suitable art means are used
to distinguish each temperature-changing element from each other
and from each of the distinctly identified data elements (to
include a stop bit).
Closed-Loop Feedback System for Heating Devices
The magnetic element temperature sensors and associated detectors
of this invention can easily be used in place of the RFID tag and
associated RFID reader/detector, respectively, in the closed-loop
temperature regulating induction heating systems described in U.S.
Pat. Nos. 6,320,169 and 6,953,919. Thus, a myriad of heating
applications may be accomplished with a temperature-regulating
magnetic element technology induction heating system which is
similar to the prior RFID systems but with the RFID components
replaced by the present sensor and detector components. For
instance, a smart range such as described in U.S. Pat. No.
6,953,919, a thermal dispensing system as described in U.S. Pat.
No. 6,822,204, a food delivery system such as described in U.S.
Pat. Nos. 6,504,135, 6,444,961, 6,274,856, and 6,232,585, and
various warming devices such as cups, bowls, sizzle platters,
plates, ski boots and other items described in U.S. Pat. No.
5,954,984 can be modified in accordance with the present invention.
Furthermore, the same components (sensor and detector) can be
integrated into other types of closed loop heating systems that are
not induction based, such as closed-loop temperature controlled
infrared, halogen and resistive heating systems.
Referring to FIG. 11, a closed-loop induction heating system 98
includes a microwire detector 46 (see FIG. 10) incorporated into an
induction heating device 100 in lieu of an RFID reader/detector.
The device 100 includes a control microprocessor 102 operably
coupled with detector 46, solid state inverter 104, and rectifier
106, as well as an induction work coil 108 coupled to inverter 104.
An AC power source 109 and current sensor 109a are operably coupled
with rectifier 106. The field generator and receiving coils 50 and
52 are integrated into a sensor component 110 located beneath a
support element 112.
The system 98 is designed to control the temperature of a graphite
heating disk 114 such as described in U.S. Pat. No. 6,657,170
having on or more embedded microwire sensors 116 of the present
invention. The disk 114 has graphite layers 118 above and below
sensor 116 as shown. Of course, any other induction-heatable object
can be controlled instead of the disk 114, such as a multiple-ply
cooking utensil (pot or pan, for example) having one or more
embedded sensors 116 therein. The feedback of temperature
information from the sensor(s) 116 is detected by the detector 46
and this information can be used to control the induction heating
of disk 114 via control microprocessor 102. If desired, the
microwire sensors and detectors of the invention may be used to
control other types of heating devices such as halogen or resistive
heaters, microwave ovens, or gas or electric ranges as described
below with other embodiments of the invention.
Temperature Sensor Sticker
In another aspect of the invention illustrated in FIGS. 12-22, a
temperature sensor similar to the ones described above is
incorporated into an adhesive-backed "sticker" 120 that can be
quickly and easily adhered to an existing piece of servingware 121
such as a plate, dish, pan, pot, bowl, tray, glass, etc. Once such
a temperature sensor sticker is adhered to a piece of servingware,
the servingware may be placed on or in the vicinity of an induction
heater, heat lamp assembly, steam heating unit, microwave oven, or
other type heating unit equipped with a re-magnetization response
detector or other type detector. The detector interrogates the
temperature sensor to sense the presence of the servingware, the
type of serving ware, and temperature data for the servingware. A
controller coupled with the detector and heating unit receives
signals from the detector which are indicative of the temperature,
or temperature range, of the servingware and which are used to
control the cycling or other operational parameter of the heating
unit. Thus, the temperature of the servingware may be continuously
or periodically monitored, and the heating unit may be controlled
so as to heat the servingware to a desired temperature range and to
maintain it within the temperature range.
Referring to FIGS. 12-15, an embodiment of a temperature sensor
sticker 120 maybe formed by adhering a microwire sensor 122 or a
plurality of such microwire sensors to a substrate 124 with an
adhesive 126 and then covering the exposed face of the adhesive
with a release layer 128. When the release layer is removed, the
temperature sensor sticker may be adhered to a piece of servingware
121 so that the servingware (and food placed thereon) may be
monitored and heated as described below.
In more detail, the microwire sensor 122 is preferably a
glass-coated amorphous magnetic microwire sensor as described
above. The temperature sensor 120 may include only one microwire
sensor 122 as shown or may include several. Each microwire sensor
122 preferably comprises a plurality of parallel microwires 130 as
best shown in FIG. 14. The number of microwires in each microwire
sensor 122 depends upon the desired operating range of the
temperature sensor 120 as well as the number of bits of data
storage required. The individual microwires 130 are preferably
small in diameter, approximately 25-35 microns, and between 10-40
mm in length. This allows the overall temperature sensor 120 to be
relatively thin and small in diameter as discussed below.
The microwires 130 making up the microwire sensor 122 can store
data or information relating to the servingware to which the
temperature sensor 120 is attached. For example, the microwires may
store data indicating the type and size of the servingware, heating
properties for the servingware (e.g. its thermal conductivity and
mass), the type of food typically placed on the servingware, and a
desired temperature or temperature range for the servingware. Each
temperature sensor 120 may store data unique to the particular
servingware to which it is attached so that each piece of
servingware (and food thereon) can be heated appropriately.
The substrate 124 holds the entire temperature sensor 120 together
and provides the individual microwires 130 a semi-stiff structure
to be aligned with when the temperature sensor 120 is assembled.
The substrate 124 also allows the temperature sensor 120 to be
easily handled, oriented, and placed upon the servingware 121. The
substrate 124 is preferably circular with a diameter of
approximately 20 mm and a thickness of 0.005 inches, but it may be
formed in other shapes and sizes without departing from the scope
of the present invention, The substrate 124 can be formed of any
suitable material but is preferably formed of polymer film material
such as PET, polyethylene, polypropylene, etc. or a cellulose,
paper, or other pulp-type material.
The substrate 124 can remain permanently upon the servingware 121
or can be chosen from a material that dissolves in water. If the
substrate 124 is designed to remain with the servingware 121, it is
preferably formed of translucent film with a continuous use
temperature greater than that of the servingware to which it is
attached. For a dissolvable substrate, the substrate may be formed
of a material similar to that of DissolvX.TM. labels by Paxar. Such
labels simply disintegrate in a dishwasher at any temperature
within seconds. Several other companies such as Spectrim Label and
Equipment, Inc. also sell dissolvable labels that are suitable for
the substrate.
The adhesive 126 serves several purposes. First, it secures the
microwires 130 which from the microwire sensor 122 to the substrate
124 in a proper orientation. Second, it allows the entire
temperature sensor sticker 120 to be affixed permanently to a piece
of servingware 121 when the release layer 128 is removed. The type
of adhesive used preferably has the following properties: 1) it
should firmly bond the microwires 130 to the servingware, 2) it
should survive long-term in the use environment of the servingware
(i.e. be resistant to the cleaning solvents used, be capable of
operating at the use temperature of the servingware, etc.), and 3)
it should be easily cured in minimal time.
In one embodiment of the temperature sensor 120, the adhesive 126
is cured within seconds by an ultraviolet light source, and the
substrate 124 dissolves away the first time the servingware 121 is
washed in water. Just about any adhesive may be used, an example of
which is selected from the DYMAX OP Series family of Ultraviolet
light (UV) curable optical assembly adhesives from a company called
DYMAX. These adhesives are optically clear, high strength, low
stress high performance UV curable optical assembly adhesives that
cure in seconds upon exposure to UV light. DYMAX OP Series UV cure
resins are single component, low outgassing, low shrinkage resins
that have a gap filling capability to 1/4 inch or more, as well as
a long room temperature shelf life. They are ideal for applications
such as the attachment of ceramic, glass, quartz, metal and plastic
components to glass. The release layer 128 may be formed of any
suitable material such as a film selected from either the
Dupont.RTM. Tedlar.RTM. family of polyvinyl fluoride films or the
3M Fluoropolymer, 2.9 Mil Medical Release Liner 9956.
Referring to FIG. 15, the thickness of the adhesive 126 between the
substrate 124 and the release layer 128 need not be much more than
the diameter of the individual microwires 130. For example, the
thickness of the adhesive layer 126 may be approximately 30-50
microns when used with microwires 130 that are approximately 30
microns in diameter. The thickness of the release film is
approximately 0.003 inches. The overall thickness of the
temperature sensor 120 (with the release layer attached) is
preferably approximately 0.01 inches, but may be between 0.005-0.03
inches.
The temperature sensor 120 may be assembled by machine using means
known widely in the art to pick and place wires onto adhesive layer
substrates. Many temperature sensors are advantageously made on one
large substrate sheet with one large release liner and then
individual temperature sensors are die-cut out of the large
sheet.
Once assembled, the temperature sensors 120 can be quickly and
easily affixed to any type of servingware. FIG. 12 shows a
dinnerware plate 121 with a temperature sensor 120 affixed to the
bottom of the plate within the plate's foot 123 or lower rim. The
dinner plate is shown as an example only, as the temperature sensor
120 may be affixed to any type of servingware.
Before attaching the temperature sensor 120, the attachment area of
the servingware 121 should first be cleaned to remove oils or other
contaminants that may prevent bonding of the adhesive. If the
servingware is a dinnerware plate or similar object, it may simply
be washed in a dishwasher. Referring to FIGS. 13 and 14, the
release layer 128 is then removed to expose one face of the
adhesive layer 126. The entire temperature sensor 120 is then
placed on the servingware with the exposed adhesive face against
the servingware.
A UV light curing spot lamp such as the BlueWave.RTM. 200 UV Light
Curing Spot Lamp from DYMAX.RTM. Corporation may then be used to
cure the adhesive. The lightguide of the curing lamp is focused on
the substrate and after approximately 5 seconds of exposure, the
adhesive layer 126 is cured and the microwires 130 making up the
microwave sensor 122 are permanently bonded to the underside of the
plate 121.
These steps maybe repeated for other plates or servingware, then
all the servingware may be placed in a dishwasher. If the substrate
126 is formed of dissolvable material, it will dissolve in the
dishwasher, leaving behind just the thin microwires 130 and the
thin adhesive layer 126 as shown in FIG. 12. The plates or other
servingware are now ready for use within a servingware warming
system described below.
The specific process for affixing the temperature sensors 120 to
the servingware may be modified. For example, a different cleaning
solvent may be used to prepare the application area on the
servingware. When adhesives other than UV-curable adhesives are
used, a heat cure or air temperature cure, rather than the UV light
cure, may be used, or the adhesive may not require any curing.
Finally, the substrate 126 may be permanent rather than
dissolvable, thus requiring no dissolving step in the process.
Various Embodiments of The Servingware Warming System
Once the temperature sensors 120 are assembled and adhered to the
servingware, one or more pieces of the servingware with food
thereon may be kept warm by a servingware warming system described
below. Each embodiment of the servingware warming system comprises
a heating unit of some kind whose power output is controlled, at
least in part, by information read from the temperature sensor 120
on a piece of servingware. The servingware warming system employs a
temperature feedback, closed-loop control method described in more
detail below. Although a specific piece of servingware may be shown
as the preferred servingware for each embodiment below, the
embodiments may use various sizes, shapes, or types of servingware,
as long as the servingware is fitted with a temperature sensor
120.
Flat-Surfaced Halogen Heater Equipped with a Microwire
Reader/Detector for Closed-Loop Temperature Feedback
FIG. 16 illustrates a servingware warming system 132 comprising a
flat-surfaced halogen heater 134 such as that marketed by Deni or
such as the Aroma PHP-323 Electric Halogen Range, in electronic
communication with a microwire reader/detector 136 whose antenna
138 is in communication with a temperature sensor 120 on a piece of
servingware 121. The halogen heater 134 includes a power supply and
control circuitry 140, a halogen heater control microprocessor 142,
an inner ring-type halogen lamp 144, an outer ring-type halogen
lamp 146, a reflective light guide 148, and a flat surface top 150
upon which the servingware 121 rests. The power supply and control
circuitry 140 gets its power from a conventional alternating
current power supply 152 and thereafter uses the electricity to
provide power to the inner and outer halogen lamps 144, 146,
wherein the amount of power is determined by the control
microprocessor 142 and is affected by switching/rheostat control
within the control circuitry 140.
The halogen lamps 144, 146 may be dimmed or shut off completely
with a very fast reaction time after commands from the
microprocessor 142 are acted upon by the switching/rheostat control
within the control circuitry 140. Since the thermal mass of the top
150 is small, and most plates and many other types of servingware
have a raised rim 123 or foot that prevents the majority of the
servingware from touching the top 150, the thermal energy transfer
between the halogen heater 134 and the servingware 121 is
essentially all via radiation. Thus, since halogen lamps have their
power output nearly instantaneously adjusted by the microprocessor
142, temperature regulation of the servingware 121 on the top 150
is possible with good precision.
Once the halogen heater unit 134 is plugged in and turned on, the
microwire reader/detector 136 sends out a pulse of low frequency
current to its associated antenna 138, which then produces a pulse
of low frequency interrogation magnetic field once per second or at
some other interval. If no servingware 121 is on the top 150, the
microprocessor 142 does not allow the power supply and control
circuitry 140 to output power to the halogen lamps 144, 146. Once a
piece of servingware 121 with a temperature sensor 120 is placed on
the top 150, the microwire reader/detector 136 senses the presence
of the servingware and reads the data stored on the temperature
sensor 120. As discussed above, this data may indicate the size of
the servingware, heating properties of the servingware such as its
thermal conductivity and mass, the type of food that is typically
placed on the servingware, a desired temperature or temperature
range for the servingware, and any other useful information. The
microprocessor may then use this data to control the heating unit
134. For example, the microprocessor 142 may use the size
information to determine whether the outside ring-type halogen lamp
146 needs to be turned on (for larger pieces of servingware that
need a large heated surface area) or if only the inner ring-type
halogen lamp 144 needs to be turned on. The light reflector 148
ensures that if only the inner ring-type halogen lamp 144 is on the
light is only directed directly above the inner-ring lamp. This
keeps the outside edge of the servingware relatively cool (except
by minimal conduction from the center of the plate) so that the
servingware may be picked up by a waiter, waitress, or other person
without burning the person's hands.
Once the microprocessor 142 determines the size of servingware and
desired temperature range, the microwire reader/detector 136 and
antenna 138 continues to interrogate the temperature sensor 120
once per second or at any other interval so as to determine the
temperature of the servingware. This temperature information is
used to determine how much power to apply to the halogen lamp(s)
144 and/or 146. Changing the intensity of the lamps 144, 146 or
simply cycling the lamps on and off in some variable duty cycle,
based upon temperature feedback, allows the halogen heater 134 to
regulate the temperature of the servingware 121 at the pre-coded
temperature of the temperature sensor 120. When the servingware is
removed from the top 150, the microwire reader/detector 136
determines that the temperature sensor is no longer present and
thus communicates with the halogen heater's microprocessor 142
which shuts off current to the halogen lamps 144, 146.
Heat Lamp System Employing a Microwire Reader/Detector for
Closed-Loop Temperature Feedback
A common radiation heating method used by restaurants to keep
single-serving food portions warm is to use one or more "heat
lamps" that are most often positioned above a table or counter upon
which full plates of food are set while waiting for a waiter or
waitress to deliver the plates to customers. "Heat lamps" as used
herein may include infrared emitters, halogen lamps, halogen
lights, infrared bulbs, infrared tubes, or infrared lamps. Heat
lamps use relatively low amounts of energy, heat quickly, and are
low cost. Infrared emitters differ from standard illuminating lamps
in their low filament temperature, resulting in much less light and
more infrared radiation.
Heat lamps are often simply halogen bulbs within a metal focuser
enclosure, whereby the infrared radiation is focused like a
spotlight down onto plates of food. Halogen lamps, bulbs, tubes and
other forms of emitter produce more than 80% of their heat in
radiant form at the short wave end of the electromagnetic spectrum.
Consequently this energy is transmitted through air with little
loss, only being absorbed by the food and plate at which it is
shined.
FIG. 17 illustrates an exemplary servingware warming system 154
utilizing a heat lamp 156 such as the model DL-750-CL heat lamp
sold by the Hatco Corporation. Electric current to the beat lamp is
controlled by a halogen power supply and control circuitry 158
which in turn takes its instructions from a control microprocessor
160. The control microprocessor 160 communicates with a
reader/detector 162 which is connected to a transmitting and
receiving antenna 164. A glass or thin non-ferromagnetic counter
166 supports servingware 121 equipped with a temperature sensor
120. The heat lamp embodiment of the servingware warming system
operates substantially the same as the flat-surface halogen heater
embodiment described above except for the differences in the
heating technologies. Namely, the heat lamp 156 is cycled on and
off by the microprocessor 160 and power supply and control
circuitry 158 at least partly due to information read from the
temperature sensor 120 by the reader/detector 162.
Magnetic Induction Equipped Food Well Employing Microwire
Reader/Detector and Utilizing Induction-Hearable Food Pans for
Closed-Loop Temperature Feedback
FIG. 18 illustrates an embodiment of a servingware warming system
which utilizes an induction heating system 168 including induction
coils or elements 170, an induction power supply and control
circuitry 172 connected to a conventional power source 174, a
microprocessor or other control unit 176, and a microwire
reader/detector 178 and associated antenna 180. In this embodiment,
the servingware is a pan 182 which can be placed in a food well
184.
To minimize costs, only one microwire reader/detector 178 and
associated antenna 180 is required per food well 184. Each food pan
182 has two temperature sensors 120 attached at the small-dimension
ends of the food pan. The temperature sensors 120 can of course be
attached to other parts of the pan 182 so long as they can be
interrogated by the reader/detector 178 and antenna 180.
The food pan 182 may be constructed by using a polymer pan body
material such as polyethersulfone or polyimide. As illustrated in
FIG. 19, a copper trace resistive grid 186 is bonded to the outside
surface of the pan so as to form a continuous circuit whose pathway
traces over all sides of the pan. On the two small-dimension ends
of the food pan reside the susceptor-portion of the copper
resistive circuit grid. This susceptor-portion is designed to have
enough of an inductance so as to couple well magnetically with the
work coil 170 of the induction heating unit 168. On each of the
susceptor portion sides, near the bottom edge of the pan, is
attached a temperature sensor 120 across several of the copper
resistive grid traces so that the temperature sensor 120 is assured
thermal contact with at least one copper trace. Since the copper
traces are identical in cross sectional area they should heat at an
identical rage. Thus, if the resistive grid is applied over the pan
surface in a uniform density, the heating of the pan should be
even.
The operation of the magnetic induction-equipped food well system
is nearly identical to the heat lamp embodiment except for the
differences in heating technologies. Namely, the servingware 182,
made with the attached complete-circuit heating grid 186 shown in
FIG. 19, is inductively heated over its entire surface to a uniform
temperature by the induction heater 168, which is controlled by
information read from the temperature sensor 120 attached to the
pan's heating grid by the microwire reader/detector 178 in
communication with the control circuitry 172. Heating is
accomplished by inducing current to flow along the resistive grid
186 by magnetically coupling the induction work coil 170 to the
susceptor-end of the microwire sensor-equipped food pan. This
induced current fosters Joule heating along the surface area of the
pan, which is in turn conducted through the pan to the food
therein.
Water Bath Food Well Equipped with Microwire Reader/Detector for
Closed-Loop Temperature Feedback
A common device used by restaurants to keep food in multi-serving
portions warm is a "steam table." A steam table is a table in which
one or more containers of food (usually rectangular pans) are kept
warm by hot water or steam circulating below the pans within a
"food well". The steam table may only accommodate one food
container or it may accommodate many food pans for buffet style
service. Often, the food well has a Calrod resistive heating
element within the water bath that heats the water to a high
temperature, often high enough to convert the water to steam, so as
to keep the food pan within the food well, and thus the food
therein, warm. For single food well systems such as buffet chafing
dish systems, a can of petroleum material is often used to heat the
water within the food well. The food pans themselves are typically
made from either stainless steel or high temperature polymer
materials such as polyethersulfone or polyimide.
FIGS. 20 and 21 illustrate a steam table 188 embodiment of the
servingware warming system. hi this embodiment, the servingware is
a pan 190 placed in a standard water-bath food well 192 such that
the pan is heated over its entire surface by steam generated by a
submersed Calrod element 194. The power of the Calrod element 194
is controlled by a power supply and control circuitry 196 which in
turn is controlled by a microprocessor or other control unit 198 at
least partially in response to data read from a temperature sensor
120 on the pan by a reader/detector 200 and its associated antenna
202.
To minimize costs, only one microwire reader/detector 200 and
associated antenna 202 is required per food well 192. Each food pan
190 has two temperature sensors 120 attached to the small-dimension
ends of the food pan (the pans are typically rectangular in shape),
but the temperature sensors may be placed elsewhere as long as they
can be interrogated by the reader/detector 200 and antenna 202.
The operation of the steam table embodiment 188 is virtually
identical to the heat lamp embodiment, except for the differences
in heating technologies.
Microwave Oven Equipped with Microwire Reader/Detector
FIG. 22 illustrates a microwave oven 204 embodiment of the
servingware warming system. In this embodiment, the servingware may
be a serving dish 206, bowl, plate, browning device that employs
microwave-susceptible materials, or any other microwave-safe food
holder. The sensor-applied servingware 206 is placed in the
microwave oven 204 whose magnetron 208 power output is controlled
by a power supply and control circuitry 210 which is in turn
controlled by a microprocessor or other control device 212 in
accordance with information read from the temperature sensor 120 by
a microwire reader/detector 214 and its associated antenna 216. It
is important to note that the inner microwave housing should be
made with thin non-magnetic sheet metal so that the microwire
antenna 216 may be placed on the outside of the microwave's inner
housing. The low transmit and receive frequency (near 100 to 300
Hz) allows the temperature sensor 120 to be read successfully by
the microwire antenna 216. It is also important to note that the
antenna 216 should be as large in surface diameter as the bottom
floor of the microwave so as to achieve the maximum read range as
well as to ensure that the user may place the servingware 206 at
any location within the microwave 204 and still achieve
communication between the temperature sensor 120 and the antenna
216.
The operation of this microwave embodiment is virtually identical
to that of the heat lamp embodiment, except for the differences in
heating technologies. Since most microwaves control their output
power by variable duty cycling of the magnetron's power, it is
possible to synchronize the communication periods of the
reader/detector 214, antenna 216, and temperature sensor 120 to the
off-times of the magnetron's duty cycle. This allows the
reader/detector 214 to communicate successfully with the
temperature sensor 120 despite the microwave radiation within the
microwire heater.
Although the invention has been described with reference to the
preferred embodiment illustrated in the attached drawing figures,
it is noted that equivalents may be employed and substitutions made
herein without departing from the scope of the invention as recited
in the claims. For example, the temperature sensor 120 may be
formed of materials and in shapes and sizes not disclosed herein
without departing from the scope of the claims.
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